1 Chapter 1 Introduction to Operating Systems Outline

1 Chapter 1 – Introduction to Operating Systems Outline 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1. 9 1. 10 1. 11 1. 12 Introduction What Is an Operating System? Early History: The 1940 s and 1950 s The 1960 s The 1970 s The 1980 s History of the Internet and World Wide Web The 1990 s 2000 and Beyond Application Bases Operating System Environments Operating System Components and Goals 1. 12. 1 Core Operating System Components 1. 12. 2 Operating System Goals 2004 Deitel & Associates, Inc. All rights reserved.

2 Chapter 1 – Introduction to Operating Systems Outline (continued) 1. 13 Operating System Architectures 1. 13. 1 Monolithic Architecture 1. 13. 2 Layered Architecture 1. 13. 3 Microkernel Architecture 1. 13. 4 Networked and Distributed Operating Systems 2004 Deitel & Associates, Inc. All rights reserved.

3 Objectives • After reading this chapter, you should understand: – – – what an operating system is. a brief history of operating systems. a brief history of the Internet and the World Wide Web. core operating system components. goals of operating systems. operating system architectures. 2004 Deitel & Associates, Inc. All rights reserved.

4 1. 1 Introduction • Unprecedented growth of computing during the past several decades. • Desktop workstations execute billions of instructions per second (BIPS) • Supercomputers can execute over a trillion instructions per second • Computers are now employed in almost every aspect of life. 2004 Deitel & Associates, Inc. All rights reserved.

5 1. 2 What Is an Operating System? • Some years ago an operating system was defined as the software that controls the hardware. • Landscape of computer systems has evolved significantly, requiring a more complicated definition. • Applications are now designed to execute concurrently. 2004 Deitel & Associates, Inc. All rights reserved.

6 1. 2 What Is an Operating System? • Separates applications from the hardware they access – Software layer – Manages software and hardware to produce desired results • Operating systems primarily are resource managers – Hardware • • Processors Memory Input/output devices Communication devices – Software applications 2004 Deitel & Associates, Inc. All rights reserved.

7 1. 3 Early History: The 1940 s and 1950 s • Operating systems evolved through several phases – 1940 s • Early computers did not include operating systems – 1950 s • Executed one job at a time • Included technologies to smooth job-to-job transitions • Single-stream batch-processing systems • Programs and data submitted consecutively on tape 2004 Deitel & Associates, Inc. All rights reserved.

8 1. 4 The 1960 s • 1960 s – Still batch-processing systems – Process multiple jobs at once • Multiprogramming – One job could use processor while other jobs used peripheral devices – Advanced operating systems developed to service multiple interactive users • 1964 – IBM announced System/360 family of computers 2004 Deitel & Associates, Inc. All rights reserved.

9 1. 4 The 1960 s • Timesharing systems – Developed to support many simultaneous interactive users – Turnaround time was reduced to minutes or seconds • Time between submission of job and the return of its results – Real-time systems • Supply response within certain bounded time period – Improved development time and methods • MIT used CTSS system to develop its own successor, Multics – TSS, Multics and CP/CMS all incorporated virtual memory • Address more memory locations than actually exist 2004 Deitel & Associates, Inc. All rights reserved.

10 1. 5 The 1970 s • Primarily multimode timesharing systems – Supported batch processing, timesharing and real-time applications – Personal computing only in incipient stages • Fostered by early developments in microprocessor technology • Department of Defense develops TCP/IP – Standard communications protocol – Widely used in military and university settings – Security problems • Growing volumes of information passed over vulnerable communications lines. 2004 Deitel & Associates, Inc. All rights reserved.

11 1. 6 The 1980 s • 1980 s – Decade of personal computers and workstations – Computing distributed to sites at which it was needed – Personal computers proved relatively easy to learn and use • Graphical user interfaces (GUI) – Transferring information between computers via networks became more economical and practical 2004 Deitel & Associates, Inc. All rights reserved.

12 1. 6 The 1980 s • Client/server computing model became widespread – Clients request various services – Servers perform requested services • Software engineering field continued to evolve – Major thrust by the United States government aimed at tighter control of Department of Defense software projects • Realizing code reusability • Greater degree of abstraction in programming languages • Multiple threads of instructions that could execute independently 2004 Deitel & Associates, Inc. All rights reserved.

13 1. 7 History of the Internet and World Wide Web • Advanced Research Projects Agency (ARPA) – Department of Defense – In late 1960 s, created and implemented ARPAnet • • Grandparent of today’s Internet Networked main computer systems of ARPA-funded institutions Capable of near-instant communication via e-mail Designed to operate without centralized control 2004 Deitel & Associates, Inc. All rights reserved.

14 1. 7 History of the Internet and World Wide Web • Transmission Control Protocol/Internet Protocol – Set of rules for communicating over ARPANet – TCP/IP manages communication between applications – Ensure that messages routed properly from sender to receiver • Error-correction – Later opened to general commercial use 2004 Deitel & Associates, Inc. All rights reserved.

15 1. 7 History of the Internet and World Wide Web • World Wide Web (WWW) – – Locate and view multimedia-based documents on almost any subject Early development begun in 1989 at CERN by Tim Berners-Lee Technology for sharing information via hyperlinked text documents Hyper. Text Markup Language (HTML) • Defines documents on WWW – Hypertext Transfer Protocol (HTTP) • Communications backbone used to transfer documents across WWW 2004 Deitel & Associates, Inc. All rights reserved.

16 1. 8 The 1990 s • Hardware performance improved exponentially – Inexpensive processing power and storage • Execute large, complex programs on personal computers. • Economical machines for extensive database and processing jobs • Mainframes rarely necessary – Shift toward distributed computing rapidly accelerated • Multiple independent computers performing common task 2004 Deitel & Associates, Inc. All rights reserved.

17 1. 8 The 1990 s • Operating system support for networking tasks became standard – Increased productivity and communication • Microsoft Corporation became dominant – Windows operating systems • Employed many concepts used in early Macintosh operating systems • Enabled users to navigate multiple concurrent applications with ease. • Object technology became popular in many areas of computing – Many applications written in object-oriented programming languages • For example, C++ or Java – Object-oriented operating systems (OOOS) • Objects represent components of the operating system – Concepts such as inheritance and interfaces • Exploited to create modular operating systems • Easier to maintain and extend than systems built with previous techniques 2004 Deitel & Associates, Inc. All rights reserved.

18 1. 8 The 1990 s • Most commercial software sold as object code – The source code not included – Enables vendors to hide proprietary information and programming techniques • Free and open-source software became increasingly common in the 1990 s – Open-source software distributed with the source code • Allows individuals to examine and modify software • Linux operating system and Apache Web server both open-source • Richard Stallman launched the GNU project – Recreate and extend tools for AT&T’s UNIX operating system – He disagreed with concept of paying for permission to use software 2004 Deitel & Associates, Inc. All rights reserved.

19 1. 8 The 1990 s • Open Source Initiative (OSI) – Founded to further benefits of open-source programming – Facilitates enhancements to software products • Permits anyone to test, debug and enhance applications – Increases chance that subtle bugs will be caught and fixed • Crucial for security errors which need to be fixed quickly – Individuals and corporations can modify the source • Create custom software to meet needs of certain environment 2004 Deitel & Associates, Inc. All rights reserved.

20 1. 8 The 1990 s • Operating systems became increasingly user friendly – GUI features pioneered by Apple widely used and improved – “Plug-and-play” capabilities built into operating systems • Enable users to add and remove hardware components dynamically • No need to manually reconfigure operating system 2004 Deitel & Associates, Inc. All rights reserved.

21 1. 9 2000 and Beyond • Middleware – Links two separate applications • Often over a network and between incompatible machines – Particularly important for Web services • Simplifies communication across multiple architectures • Web services – Encompass set of related standards – Ready-to-use pieces of software on the Internet – Enable any two applications to communicate and exchange data 2004 Deitel & Associates, Inc. All rights reserved.

22 1. 10 Application Bases • IBM PC immediately spawned a huge software industry – Independent software vendors (ISVs) market software packages to run under MS-DOS operating system. – Operating system must present environment conducive to rapid and easy application development • Otherwise unlikely to be adopted widely • Application base – Combination of hardware and operating system used to develop applications – Developers and users unwilling to abandon established application base • Increased financial cost and time spent relearning 2004 Deitel & Associates, Inc. All rights reserved.

23 1. 10 Application Bases Figure 1. 1 Interaction between applications and the operating system. 2004 Deitel & Associates, Inc. All rights reserved.

24 1. 11 Operating System Environments • Operating systems intended for high-end environments – Special design requirements and hardware support needs • Large main memory • Special-purpose hardware • Large numbers of processes • Embedded systems – Characterized by small set of specialized resources – Provide functionality to devices such as cell phones and PDAs – Efficient resource management key to building successful operating system 2004 Deitel & Associates, Inc. All rights reserved.

25 1. 11 Operating System Environments • Real-time systems – Require that tasks be performed within particular (often short) time frame • Autopilot feature of an aircraft must constantly adjust speed, altitude and direction – Such actions cannot wait indefinitely—and sometimes cannot wait at all 2004 Deitel & Associates, Inc. All rights reserved.

26 1. 11 Operating System Environments • Virtual machines (VMs) – Software abstraction of a computer – Often executes on top of native operating system • Virtual machine operating system – Manages resources provided by virtual machine • Applications of virtual machines – Allow multiple instances of an operating system to execute concurrently – Emulation • Software or hardware mimics functionality of hardware or software not present in system – Promote portability 2004 Deitel & Associates, Inc. All rights reserved.

27 1. 11 Operating System Environments Figure 1. 2 Schematic of a virtual machine. 2004 Deitel & Associates, Inc. All rights reserved.

28 1. 12 Operating System Components and Goals • Computer systems have evolved – – Early systems contained no operating system, Later gained multiprogramming and timesharing machines Personal computers and finally truly distributed systems Filled new roles as demand changed and grew 2004 Deitel & Associates, Inc. All rights reserved.

29 1. 12. 1 Core Operating System Components • User interaction with operating system – Often, through special application called a shell – Kernel • Software that contains core components of operating system • Typical operating system components include: – – – Processor scheduler Memory manager I/O manager Interprocess communication (IPC) manager File system manager 2004 Deitel & Associates, Inc. All rights reserved.

30 1. 12. 1 Core Operating System Components • Multiprogrammed environments now common – Kernel manages the execution of processes – Program components which execute independently but use single memory space to share data are called threads. – To access I/O device, process must issue system call • Handled by device driver • Software component that interacts directly with hardware • Often contains device-specific commands 2004 Deitel & Associates, Inc. All rights reserved.

31 1. 12. 2 Operating System Goals • Users expect certain properties of operating systems – – – – – Efficiency Robustness Scalability Extensibility Portability Security Protection Interactivity Usability 2004 Deitel & Associates, Inc. All rights reserved.

32 1. 13 Operating System Architectures • Today’s operating systems tend to be complex – Provide many services – Support variety of hardware and software – Operating system architectures help manage this complexity • Organize operating system components • Specify privilege with which each component executes 2004 Deitel & Associates, Inc. All rights reserved.

33 1. 13. 1 Monolithic Architecture • Monolithic operating system – Every component contained in kernel • Any component can directly communicate with any other – Tend to be highly efficient – Disadvantage is difficulty determining source of subtle errors 2004 Deitel & Associates, Inc. All rights reserved.

34 1. 13. 1 Monolithic Architecture Figure 1. 3 Monolithic operating system kernel architecture. 2004 Deitel & Associates, Inc. All rights reserved.

35 1. 13. 2 Layered Architecture • Layered approach to operating systems – Tries to improve on monolithic kernel designs • Groups components that perform similar functions into layers – Each layer communicates only with layers immediately above and below it – Processes’ requests might pass through many layers before completion – System throughput can be less than monolithic kernels • Additional methods must be invoked to pass data and control 2004 Deitel & Associates, Inc. All rights reserved.

36 1. 13. 2 Layered Architecture Figure 1. 4 Layers of the THE operating system. 2004 Deitel & Associates, Inc. All rights reserved.

37 1. 13. 3 Microkernel Architecture • Microkernel operating system architecture – Provides only small number of services • Attempt to keep kernel small and scalable – High degree of modularity • Extensible, portable and scalable – Increased level of intermodule communication • Can degrade system performance 2004 Deitel & Associates, Inc. All rights reserved.

38 1. 13. 3 Microkernel Architecture Figure 1. 5 Microkernel operating system architecture. 2004 Deitel & Associates, Inc. All rights reserved.

39 1. 13. 4 Networked and Distributed Operating Systems • Network operating system – Runs on one computer – Allows its processes to access resources on remote computers • Distributed operating system – Single operating system – Manages resources on more than one computer system – Goals include: • • Transparent performance Scalability Fault tolerance Consistency 2004 Deitel & Associates, Inc. All rights reserved.

40 1. 13. 4 Networked and Distributed Operating Systems Figure 1. 6 Client/server networked operating system model. 2004 Deitel & Associates, Inc. All rights reserved.